Ten thousand marks of his ransom were remitted as Jane's dowry, and in April 1424 James and his bride entered Scotland. With the reign of James I., whose coronation took place at Scone on the 21st of May 1424, constitutional sovereignty may be said to begin in Scotland. By the introduction of a system of statute law, modelled to some extent on that of England, and by the additional importance assigned to parliament, the leaven was prepared which was to work towards the destruction of the indefinite authority of the king, and of the unbridled licence of the nobles. During the parliament held at Perth in March 1425 James arrested Murdoch, duke of Albany, and his son, Alexander; together with Albany's eldest son, Walter, and Duncan, earl of Lennox, who had been seized previously; they were sentenced to death, and the four were executed at Stirling. In a parliament held at Inverness in 1427 the king arrested many turbulent northern chiefs, and his whole policy was directed towards crushing the power of the nobles. In this he was very successful. Expeditions reduced the Highlands to order; earldom after earldom was forfeited; but this vigour aroused the desire for revenge, and at length cost James his life. Having been warned that he would never again cross the Forth, the king went to reside in Perth just before Christmas 1436. Among those whom he had angered was Sir Robert Graham (d. 1437), who had been banished by his orders. Instigated by the king's uncle, Walter Stewart, earl of Atholl (d. 1437), and aided by the royal chamberlain, Sir Robert Stewart, and by a band of Highlanders, Graham burst into the presence of James on the night of the 20th of February 1437 and stabbed the king to death. Graham and Atholl were afterwards tortured and executed. James had two sons: Alexander, who died young, and James II., who succeeded to the throne; and six daughters, among them being Margaret, the queen of Louis XI. of France. His widow, Jane, married Sir James Stewart, the "black knight of Lorne," and died on the 15th of July 1445. During the latter part of James's reign difficulties arose between Scotland and England and also between Scotland and the papacy. Part of the king's ransom was still owing to England; other causes of discord between the two nations existed, and in 1436 these culminated in a short war. In ecclesiastical matters James showed himself merciless towards heretics, but his desire to reform the Scottish Church and to make it less dependent on Rome brought him into collision with Popes Martin V. and Eugenius IV.